This invention relates to waterbed mattresses and more particularly to such mattresses with improved corners.
Waterbed mattresses contain a large quantity of water which transmits substantial pressure throughout the interior of the mattress when a weight, such as the human body, is on the mattress. Even the weight of the water itself creates substantial pressure in the mattress.
These mattresses typically are made of a single layer of a plastic material such as vinyl. The thickness and other characteristics of the vinyl are selected to provide adequate strength to resist rupture of the mattress while at the same time providing a resilient feel to the mattress
Since a waterbed mattress cannot be formed as a single, unitary piece, it is necessary to seal various portions of the vinyl together by heat welding or the like to form the completed mattress. These seams, particularly in the corners of the mattresses, often are the weakest part of the mattress and the place where the pressure can cause the mattress to rupture. Of course, the rupture may be small, which results in a relatively minor leakage of water from the mattress. Any such leakage is, however, unacceptable.
Waterbed mattresses are also inherently flexible They change their shape when pressures are applied thereto. Thus, for example, when someone tries to place sheets on a waterbed mattress, the mattress will not lift evenly, making it difficult to do so. Sheets for waterbed mattresses typically include a pocket at each corner in which the mattress is inserted to hold the sheets in place. The flexible nature of the waterbed mattress makes it difficult to capture the mattress in these sheet pockets. It also sometimes results in the mattress corner pulling out of the sheet pocket.